Cyclic olefin polymers are well known in the art. See, for example, U.S. Pat. No. 5,087,677, and references cited therein, which describes a process for preparing cyclic olefin polymers using a catalyst system that comprises a metallocene compound and an aluminoxane. Some other patents of interest in this regard include, for example, U.S. Pat. Nos. 5,422,409; 5,324,801; 5,331,057; 4,943,611; 5,304,596 and EP 608903. Well studied cyclic olefin polymers are cyclic olefin copolymers which are copolymers of a cyclic olefin (such as, for example, norbornene) and an acyclic olefin (such as, for example, ethylene). While cyclic olefin copolymers are known to possess good mechanical and optical properties suitable to be used as engineering resins and thermoplastics, for certain applications such as, for example, optical discs, lenses and the like, improved impact resistance and elongation as well as good optical transparency would be highly desirable.
The transparency of a polymer determines its suitability for optical applications. The higher the transparency, the more suitable it is for certain applications such as, for example, lenses. The impact strength of polymers generally governs their resistance to breakage, usually when struck at high velocities, and is a measure of their toughness. Typically, the impact strength of a polymer is improved by forming suitable blends of the polymer with a suitable elastomer or elastomers to form shock-absorbing rubbery domains in the polymer. This approach is most successful when there is a strong interaction between the surface of the rubbery domains and the polymer. When one prepares blends of an optically useful polymer to improve its impact strength, one has to make sure that the transparency of the polymer is not sacrificed. It will be useful if the blends maintain or improve the transparency in addition to increased impact strength, i.e., if the blends are isorefractive to the polymer. It will also be highly desirable to preserve the processability of the polymer after blending.
Thus, it is an object of this invention to provide suitable blends of cyclic olefin polymers exhibiting improved impact resistance with a Notched Izod greater than 1 ft-lb/in.
It is an additional object of this invention to provide cyclic olefin polymers exhibiting good transparency, with an optical transmission greater than 85% and optical haze less than 10%.
It is a further object of this invention to provide cyclic olefin polymers exhibiting improved impact resistance and good transparency.
It is yet another object of this invention to provide processable cyclic olefin polymers exhibiting improved impact resistance and good transparency.
Other objects and advantages of the present invention shall become apparent from the accompanying summary, description and examples.